The thermal degradation mechanisms of random copolymers of methacrylonitrile (MAN) and styrene (St) have been investigated
by pyrolysis gas chromatography in the temperature range of 358 to 920‡C using a Curie point pyrolyzer (JHP-2) and comparing
results with the results from TG/DTA-FTIR apparatus (SII-6200, JASCO-320). The amount of St monomer from decomposition of
the copolymer is higher than that from P(St) alone; whilst that of MAN monomer from copolymer is lower than that from P(MAN).
This phenomenon reflects the boundary effect in the pyrolysis of copolymer. The thermal degradation mechanisms of copolymers
are discussed in terms of the competition between the depolymerization and the back biting reaction on the basis of bond dissociation
energies of C-C and C-H bonds in the copolymer chain.